57th IMO in Hong Kong

$\large{\begin{array}{ccccccc} && & & & & 5&7\\ && & & & I & M&O\\ && & & 2& 0 & 1&6\\ && & & & & I&N\\ +&& & & H& O & N&G\\ \hline & & & & K& O & N&G\\ \hline \end{array}}$

The above represents a cryptogram, each letter represents a distinct digit, and each leading digit is non-zero. Find the number of possible solutions to this cryptogram.

Image Credit: Queen Elizabeth Stadium, Hong Kong. 5 July, 2016.

IMO scores have been released. Congratulations to the medalists and top-scoring teams, and thanks to each and every team for joining us in this meaningful event.